Biochemical similarities between hypothyroidism and riboflavin deficiency.

Abstract

Measurements have been made of the activities of 2 flavoprotein enzymes, glycolic acid oxidase and TPN-cytochrome c reductase, in animals made either hypothyroid or riboflavin-deficient. These enzyme activities were then compared with the hepatic levels of FMN and FAD in the 2 groups of animals. In hypothyroid animals, the hepatic activities of both enzymes, as well as the concentrations of FMN and FAD, were markedly reduced below values in control animals. In riboflavin-deficient rats, these enzyme activities and also the hepatic levels of FMN and FAD were depressed even further than in hypothyroid rats. Hepatic flavokinase, which converts riboflavin to FMN, was similarly depressed in both conditions. No differences were observed in either the hepaticlevels of FMN and FAD or the hepatic activity of flavokinase between control rats which were pair-fed to the deficient animals and those which were permitted to feed ad lib. In pair-fed controls, the hepatic activity of glycolic acid oxidase was reduced to h...